Great info thanks for sharing. We all know it's not necessary to know the exact distance to the lands. However there are some of us out there that just want to know for peace of mind and have ability to accurately measure throat erosion.
Easy/accurate way to find the lands
- Thread starter BountyHunter
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I have several precision AR's. The bolt closing method doesn't work well with them.
I have become quite proficient with the stoney point. I will stick with it.
Mikecr
Well-Known Member
I don't know, it's easy but hard to declare as accurate in determining 'touching'.
His measure is of extraction resistance feel rather than touching feel.
There is ITL, TOUCHING, OTL, and JAM.
Both ITL/OTL are purely w/resp to touching, which does not leave any marks at all.
Anything beyond touching is ITL. ITL leaves marks and provides extraction resistance as a matter of wedging interface leade angle to ogive radius.
Anything soft seating the bullet is JAM.
Touching is my setting of a bullet squarely against lands with the barrel pointed down. Even with the spring force of an indicator to the bullet base, there is no wedging or marking of ogives there, it's touching..
You might wonder the use in this,, it's called the 'cleaning rod method' of determining touching COAL. There is a rig setup officially by R-P Tool(which I use), but there have been many in method.
His measure is of extraction resistance feel rather than touching feel.
There is ITL, TOUCHING, OTL, and JAM.
Both ITL/OTL are purely w/resp to touching, which does not leave any marks at all.
Anything beyond touching is ITL. ITL leaves marks and provides extraction resistance as a matter of wedging interface leade angle to ogive radius.
Anything soft seating the bullet is JAM.
Touching is my setting of a bullet squarely against lands with the barrel pointed down. Even with the spring force of an indicator to the bullet base, there is no wedging or marking of ogives there, it's touching..
You might wonder the use in this,, it's called the 'cleaning rod method' of determining touching COAL. There is a rig setup officially by R-P Tool(which I use), but there have been many in method.
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Nothing new on the R-P tool. Just a spin off of the Sinclair tool that has been around for years or cleaning rod with collars on it.
All those type rely on finger pressure and feel and can vary very easily by .015-.020
Got two laying in my box that I do not use.
All those type rely on finger pressure and feel and can vary very easily by .015-.020
Got two laying in my box that I do not use.
Rich Coyle
Well-Known Member
Are you saying one individual will get that much variation or different people will get that much in the same chamber?
Next question: If the same guy gets the same measurement every time is there a problem?
Mikecr
Well-Known Member
I should say that I'm not really knocking the method in discussion.
Any method that we can consistently do locally is probably good enough, given that the value in this determination is limited to precaution of load pressure step change.
I really think we make too much of it.
Beyond this all that matters, different subject, is the CBTO that produces best results -regardless of land relationship(xOTL, touching, xITL, jam). We don't even need to know that relationship to find it. Here again the important condition of it is consistent setting as verified locally.
Any method that we can consistently do locally is probably good enough, given that the value in this determination is limited to precaution of load pressure step change.
I really think we make too much of it.
Beyond this all that matters, different subject, is the CBTO that produces best results -regardless of land relationship(xOTL, touching, xITL, jam). We don't even need to know that relationship to find it. Here again the important condition of it is consistent setting as verified locally.
.015-.020 ?
I do this a lot. I am always trying new bullets and I have to check COL on all of them. I shoot jams a lot and need to know where the lands are.
Now I get variations of 0.002 sometimes 0.003 and I will measure at lest 5 times.
I also measure first touching and with heavy pressure even tapping the bullet into the lands.
I would say that the average variation between just touching and jammed is only 0.005.
My jammed loads are just touching plus 0.01 and I feel like that is really jammed. Could even seat the bullet a little deeper.
SidecarFlip
Well-Known Member
I have to agree with that but it will depend largely on the shape of the Ogive on how far it penetrates the rifling. Stubby pills like say a Sierra Game King won't go in as far because of the shape whereas a VLD Berger with it's long tapered ogive will penetrate a bit farther.
I just employ the Berger method. I woks well enough for me, averaging 10 insertions.
All I'm looking for is that jump for group measurement anyway. The LL dimension is the starting point. Thats it.
